Various devices have been used in an attempt to provide a relatively cool light beam to limit some of the heat problems associated with lighting apparatus and in particular, in stage lighting apparatus. Most of the heat is generated from the infrared portion of the beam. One such attempt includes a reflector made of heat resistant glass coated on one side facing the lamp with a multi-layer dielectric film forming a "cold mirror". This device reflects visible light and allows heat rays to pass through the film.
In the past, a reflector such as that described above has been thermally connected to a heat sink. In this manner, rays directed at the reflector pass through the film and glass or other suitable substrate of the reflector and strike the heat sink which absorbs the rays as heat.
Another attempt utilizes a multi-layer dielectric interference filter, i.e. a dichroic "hot mirror" and a liquid cell placed in the light beam to remove energy, in the infrared region, from the beam. The hot mirror functions to reflect "near" infrared energy while passing light in other regions. The water in the liquid cell is effective in absorbing the "far" infrared energy that is not reflected by the dichroic filter.
This combination removes infrared radiation from the beam before it reaches, for example, a commonly used special effects apparatus such as an image projection device known as a gobo or an LCD. Although water is used in this liquid cell, hydrocarbons have also been used, i.e. glycol and water-glycol mixes. However, these liquids are limited by their tendency to chemically break down after prolonged use, thus changing color. This color change can interfere with the projected image.
The foregoing illustrates limitations of the know prior art. Thus it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations as set forth above. Accordingly, a suitable alternative is provided including features and benefits more fully disclosed hereinafter.